1. Field of the Invention
The invention relates to a motor vehicle seat assembly, and more particularly to a power seat adjuster including a single motor and a multi-output transmission assembly to provide the desired adjustability of the seat assembly.
2. Description of Related Art
Motor vehicles include seat assemblies having a seat cushion and a seat back for supporting occupants within the vehicle. Most front row seat assemblies, such as driver and passenger seat assemblies, are adjustably mounted on a floor of the vehicle. It is common that such seat assemblies include power seat adjusters for adjusting the position of the seat assembly relative to the vehicle floor. A typical power seat adjuster can be operated to adjust the seat assembly in a generally horizontal or fore/aft direction and a generally vertical or up/down direction.
The generally horizontal or fore/aft direction of the seat assembly corresponds to a longitudinal axis of the vehicle. Movement of the seat assembly along the longitudinal axis moves the seat assembly closer to or farther away from the vehicle steering wheel and/or instrument panel. To allow fore and aft adjustment, the seat assembly typically includes a seat track mechanism having an upper track slidably coupled with a lower track. The upper track is attached to an underside of the seat cushion and the lower track is attached to the vehicle floor. A threaded lead screw is driven by a first electric motor and a nut translating along the lead screw is connected to and moves the upper track relative to the lower track, thereby moving the seat assembly in the fore/aft direction.
For the generally vertical or up/down direction of the seat assembly, front and rear portions of the seat cushion are typically controlled separately. A first gear mechanism is disposed between the upper track and the front portion of the seat cushion and a second gear mechanism is disposed between the upper track and the rear portion of the seat cushion. The first gear mechanism is actuated by a second electric motor to allow up and down adjustment of the front portion of the seat cushion. Similarly, the second gear mechanism is actuated by a third electric motor to allow up and down adjustment of the rear portion of the seat cushion. Thus, simultaneous actuation of the second and third electric motors moves the entire seat cushion in the up/down direction.
The power seat adjuster can also be configured to pivot or recline the seat back relative to the seat cushion. A recliner mechanism is disposed between the seat back and the seat cushion. The recliner mechanism is actuated by a fourth electric motor to allow pivotal movement of the seat back.
As described above, conventional power seat adjusters can include four or more electric motors for providing adjustment of the seat assembly. While the use of multiple electric motors is effective in adjusting the position of the seat assembly, the cost of the electric motors is relatively expensive and increases the weight and complexity of the seat assembly. It is therefore desirable to provide an improved power seat adjuster using a single motor to provide the desired adjustability of the seat assembly.